Pneumatic tube carrier systems are a well-known means for the automated transport of materials between, for example, an origination location and any one of a plurality of destination locations. A typical system includes a number of pneumatic tubes interconnected in a network to transport carriers between user stations. Various blowers and transfer units provide the force and path control means, respectively, for moving the carriers through and from tube-to-tube within the network. Generally, transfer units move or divert pneumatic carries from a first pneumatic tube to a second pneumatic tube in order to route the pneumatic carrier between locations, or stations, in the network.
The pneumatic tubes forming the network of a pneumatic carrier system may be arranged in any manner that allows the carriers to be transferred between various stations. Generally, systems include a number of individual stations interconnected to the network by a single pneumatic tube. The single pneumatic tube transfers carriers to and from the station under pressure and vacuum.
Large pneumatic carrier systems often include complex network of interconnected tubes. Further, to provide functionality to separate portions of such large systems, most such systems are divided into multiple zones. Typically, each zone includes a set of stations that receive pneumatic pressure and/or vacuum from a common blower. For instance, a transfer unit that receives pressure and/or vacuum from the common blower may connect to each station of such a zone. This transfer unit permits carriers received from a tube connected to one of the stations to be transferred to a tube connected to another of the stations. Different zones are interconnected to permit inter-zone traffic (i.e., transfers from zone to zone). Such inter-zone connections are often made using a single bi-directional tube or using a pair of unidirectional tubes. In this regard, a zone may interconnect directly to one or more zones. Accordingly, to effect transfer of a carrier from a sending station to a receiving station may require passing a carrier through more than one zone and/or multiple inter-zone connections. Often, multiple potential paths or routes exist for transferring a pneumatic carrier between an origination location and a destination location.